You can’t just store the encryption key only in memory, you would loose the ability to decrypt your data on every reboot. The encryption key gets stored on a separate physical device normally a KMS and fetched into memory only for that session. At GPTree we use a unique DEK for each user stored in a third party KMS with strict IAM policies that prevent any one person from accessing both and the MFA for the KMS held in escrow so users data remains encrypted and private even to us. For true 100% no knowledge you would need envelope encryption client side but that is not possible for us since embedding a need to be encrypted with the same keys which can only be done on source data
I've been thinking about this as well.
Would an attacker actually try that? In a mass attack they probably don't bother and just try to dump the db and move on. On a targeted attack they might ..
I've been thinking about entering the encryption keys in memory after server…
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